METHODS - 10 healthy volunteers will be randomised into two groups, in an interventional cross-over trial. Baseline measurements of haemodynamic velocity and flow will be taken, then subjects given bilateral therapy with each of the two devices in turn. Laser doppler fluximetry readings will be taken from the hand and foot. Baseline readings will be compared with readings taken after immediate cessation of therapy, and after 10 minutes. Tolerability will be measured using a verbal reported score.